Julie Ouerfelli-Ethier^1,2, Tristan Jurkiewicz², Isabella Comtois Bona¹, Thomas Carrier¹, Aarlenne Z. Khan¹, Laure Pisella²; ¹University of Montreal, ²Université Claude Bernard Lyon 1

Spatial and response inhibition are two different types of inhibition processes. Spatial inhibition refers to the suppression of a specific location whereas response inhibition involves the cancellation of a motor response according to changing contextual demands and is thus motor based. While these two types of inhibition are conceptually distinct, it is unclear if they recruit overlapping or distinct neuronal substrates. Previous findings have pointed to a role of the dorsal posterior parietal cortex (PPC) in spatial rather than response inhibition in an anti-saccade task, involving both types of inhibition. Here we examined the effects of lesions on the dorsal PPC on performance during two saccade tasks separately measuring spatial inhibition (inhibition of return (IOR) task) and response inhibition (stop signal task). To do so, we tested two optic ataxia patients, one unilateral and one bilateral, with lesions to the dorsal PPC, as well as 21 age-matched controls. For our spatial inhibition task, we found the typical IOR effect in our controls, however this was absent in our patients’ ataxic hemifields. In contrast, we found no difference in performance between our patients and their respective controls on the stop signal task. These results confirm that motor-based inhibition is preserved following damage to the dorsal PPC, while spatial inhibition is impacted. Our results thus point to a specific role of the dorsal PPC in spatial inhibition, notably related to spatial attentional mechanisms.

Acknowledgements: This work was supported by the Natural Sciences and Engineer Research of Council of Canada, Unverisité de Lyon Idex mobility fund, Graduate and Postgraduate Studies and School of Optometry of University of Montreal, and Vision Health Research Network.